The invention relates to a diaphragm for a lung demand valve, in particular, although not exclusively, to a lung demand valve suitable for use in CBRN environments.
A lung demand valve (LDV) is typically used with breathing apparatus in order to control the supply of breathable gas to the user. An LDV usually comprises a flexible diaphragm that responds to pressure changes so as to control the flow of the breathable gas. A first side of the diaphragm is exposed to ambient pressure and the second side of the diaphragm is exposed to the pressure within the face-mask. The diaphragm is typically manufactured from an elastomer such as silicone.
If the LDV is to be used in chemical, biological, radiological and/or biological (CBRN) environments, it is necessary to prevent CBRN agents from being inhaled by the user. Since silicone is permeable, measures must be taken to ensure that CBRN agents cannot permeate through the diaphragm.
EP 1 575 675 A1 discloses a face-mask mechanically coupled to a LDV. The face-mask comprises a main mask and an inner mask which fits over the wearer's mouth and nose. The interior of the inner mask is in fluidic communication with the interior of the main mask by means of non-return valves. The interior of the main mask is in fluidic communication with an inlet port which is mechanically and fluidically coupled to a supply port of the LDV. The LDV includes a diaphragm and a cover which defines a passage through which exhaled air is used to flush the space around the diaphragm. Thus, any toxic or undesirable gas in the vicinity of the diaphragm is pushed out to the atmosphere by the exhaled air flowing past and around the diaphragm. This can prevent CBRN agents from accumulating on the outer surface of the diaphragm and permeating through the diaphragm.
EP 1 638 650 A1 discloses a LDV for use with breathing apparatus. The LDV has a valve assembly that includes an inlet for connection to a source of breathing gas, an outlet for connection to a face-mask to provide breathing gas to the user, and an actuator for controlling the flow of breathing gas between the inlet and the outlet in response to the user's respiration. The LDV further includes a flexible elastomeric diaphragm in operative connection with the actuator. The diaphragm is exposed to ambient pressure on a first side and exposed to a positive pressure within the face-mask on a second side. The regulator assembly also includes an impermeable and flexible shield that is spaced from the diaphragm and seals the first side of the diaphragm from certain toxic substances in the ambient atmosphere, while allowing the first side of the diaphragm to experience ambient pressure. The flexible shield moves along with the diaphragm during respiration without dampening the movement of the diaphragm during respiration of the user.
Whilst the above described arrangements may be appropriate in some circumstances, the complexity and therefore cost of the lung demand valve is increased when compared with a conventional lung demand valve.
It is therefore desirable to provide an improved arrangement.
In a broad aspect the invention concerns a CBRN or barrier layer of a diaphragm for a lung demand valve that is arranged to restrict the permeation of at least some CBRN agents through the diaphragm.
The term “CBRN” will be used throughout the description and claims and is an acronym for “chemical, biological, radiological and/or nuclear.”
According to an aspect of the invention there is provided a diaphragm for a lung demand valve, comprising: a CBRN (or barrier) layer which is sufficiently resistant to the permeation of at least some CBRN (or hazardous) agents; and a resilient layer which is resiliently deformable; wherein the CBRN (or barrier) layer is arranged to restrict the permeation of at least some CBRN (or hazardous) agents through the diaphragm, and wherein the resilient layer is arranged to allow the diaphragm to be resiliently deformed. The diaphragm may be suitable for use in at least some CBRN or hazardous environments. The CBRN layer may be referred to as a barrier layer. The resilient layer may ensure that the diaphragm responds appropriately to differential pressure changes across the diaphragm. The diaphragm may be referred to as a composite diaphragm.
The CBRN layer may prevent, restrict or inhibit certain types of CBRN agents, such as those which may typically be encountered by persons working in hazardous environments, from permeating through the diaphragm. This may ensure that a person using the lung demand valve does not inhale CBRN agents that may be present in the ambient atmosphere.
The resilient layer may ensure that the composite diaphragm is sufficiently resiliently deformable such that in use it can respond to the differential pressure changes and control the supply of breathable gas. The resilient layer may therefore act as the spring of the diaphragm. The resilient layer may be sufficiently resilient over a wide range of temperatures such that the diaphragm, and hence the lung demand valve, can operate over a wide temperature range.
The composite diaphragm may therefore have a first CBRN layer that prevents the user from inhaling hazardous CBRN agents, and a second resilient layer that ensures that the diaphragm responds appropriately to differential pressure changes over a wide temperature range.
The CBRN layer may be sufficiently resistant to the permeation of CBRN agents such that the diaphragm, and/or a lung demand valve which it is part of, complies with certain CBRN requirements. The CBRN requirements may be NIOSH 42 CFR 84.63, the entire and/or BS8468-1 2006, the entire contents of which are incorporated herein by reference.
The resilient layer may be sufficiently resiliently deformable such that the diaphragm, and/or a lung demand valve which it is part of, complies with certain requirements. The requirements may be NIOSH 42 CFR 84 and/or NFPA 1981 and/or EN137, the entire contents of each are incorporated herein by reference.
The CBRN layer may be deformable. The CBRN layer may be substantially continuous. In other words, the CBRN layer may not have any openings or holes that would allow CBRN agents to pass through the diaphragm.
The CBRN layer may comprise a plastics material. The plastics material may comprise polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) or polyether ether ketone (PEEK).
The CBRN layer may have a thickness of between 0.001-0.05 mm, or 0.002-0.03 mm, or 0.003-0.02 mm. The thickness may be less than 0.05 mm, or less than 0.03 mm, or less than 0.02 mm.
The resilient layer may be discontinuous. This may mean that the resilient layer is provided with one or more slots or openings, for example. The resilient layer may comprise at least one opening. The resilient layer may comprise a plurality of openings. The openings may be circumferentially arranged around the diaphragm. The openings may be circular and the resilient layer may be symmetrical. The resilient layer may be in the form of a web. The slots or openings may be arranged uniformly. The resilient layer may be rotationally symmetric. Further, the diaphragm may be rotationally symmetric. The resilient layer and/or the diaphragm may have rotational symmetry of order at least three. Having a discontinuous resilient layer may allow the resilient properties of the complete diaphragm to be tailored to suit the particular requirements, for example, the breathing requirements of the lung demand valve. The resilient layer may form a support structure for the CBRN layer.
The resilient layer may comprise an elastomer. The resilient layer may comprise silicone.
The resilient layer may have a thickness of between 0.1-2 mm, or 0.2-1.5 mm, or 0.3-1 mm. The thickness may be less than 2 mm, or less than 1.5 mm, or less than 1 mm, or less than 0.8 mm.
The diaphragm may comprise a sealing edge or lip that is arranged to be retained by a part of the lung demand valve so as to provide a seal preventing fluid flow across the diaphragm. The resilient layer may comprise a sealing lip that is retained in a recess of the lung demand valve.
The CBRN layer and the resilient layer may be bonded together to form a laminate. The CBRN layer and the resilient layer may be heat bonded together or may be bonded together using an adhesive.
The resilient layer may be arranged such that in use it is on the ambient side. This would mean that the resilient layer is exposed the atmosphere. The CBRN layer may be arranged such that in use it is on the fresh breathable gas side. This would mean that the CBRN layer is exposed to the breathable gas within the lung demand valve. However, it should be appreciated that the layers could be the opposite way round.
The diaphragm may further comprise a substantially rigid plate against which in use a spring and/or valve lever acts. The rigid plate may be attached to the resilient layer or the CBRN layer. The rigid plate may be adhered to either layer. The resilient layer may comprise a plate opening within which the rigid plate is located. The CBRN layer may extend across the rigid plate and may be continuous. Alternatively, the CBRN layer could be bonded to the rigid plate.
The diaphragm, the resilient layer and/or the CBRN layer may be substantially circular. The diameter of the diaphragm may be between 30-90 mm, or 40-80 mm, or 50-70 mm.
The diaphragm may have a central portion and a winged side.
The invention also concerns a lung demand valve comprising a diaphragm in accordance with any statement herein.
The invention further concerns a breathing apparatus comprising a lung demand valve in accordance with any statement herein.
According to a second aspect of the invention there is provided a method of upgrading a lung demand valve such that it is suitable for use in CBRN environments, comprising removing a conventional diaphragm from a lung demand valve, and subsequently fitting the lung demand valve with a diaphragm in accordance with any statement herein. A “conventional” diaphragm may be a diaphragm that is not CBRN compliant.
According to a further aspect of the invention there is provided a diaphragm for a lung demand valve comprising a barrier layer which is resistant to the permeation of at least some hazardous agents and a support structure that is resiliently deformable. The barrier layer may ensure that that hazardous agents, such as CBRN agents, are restricted from permeating through the diaphragm, and the support structure may ensure that the diaphragm is resiliently deformable and responds to the appropriate pressure changes.
According to yet a further aspect of the invention there is provided a lung demand valve, comprising: a main housing defining an internal chamber; a breathing port which is in fluid communication with the internal chamber and through which in use a user inhales; a breathable gas inlet which in use is connected to a supply of breathable gas; a valve assembly for controlling the supply of breathable gas to the user through the internal chamber and breathing port; a diaphragm for controlling the valve assembly and which in use responds to the inhalation and exhalation of the user; wherein the diaphragm comprises: a laminate structure comprising a continuous CBRN layer which is sufficiently resistant to the permeation of at least some CBRN agents and a discontinuous resilient layer which is resiliently deformable; wherein the CBRN layer is arranged to restrict the permeation of at least some CBRN agents through the diaphragm, and wherein the resilient layer is arranged to allow the diaphragm to be resiliently deformed.
The invention may comprise any combination of the features and/or limitations referred to herein, except combinations of such features as are mutually exclusive.